Characterization and microstructure observation of sintered red mud–fly ash mixtures at various elevated temperature

Samal, Sneha; Ray, Ajoy Kumar; Bandopadhyay, Amitava

doi:10.1016/j.jclepro.2015.04.010

Cited by 45 publications

(14 citation statements)

References 11 publications

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“…Therefore, almost all bauxite residue continues to be stored indefinitely in bauxite residue disposal areas (BRDAs) [14,15], which require on-going efforts to manage the waste and lower its potential to contaminate water, occupy land and disturb the surrounding ecology [16][17][18][19][20][21][22]. Furthermore, leaching of alkaline waste from BRDAs is an added problem [23,24]. Additionally, freshly formed alkaline dust and efflorescence at the surfaces of BRDA's that contain large amounts of sodium are directly harmful to BRDA operatives [25].…”

Section: Introductionmentioning

confidence: 99%

Acid transformation of bauxite residue: Conversion of its alkaline characteristics

Kong

Xue

et al. 2017

Journal of Hazardous Materials

131

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Graphical abstractHighlights  Speciation and transformation of solid and soluble alkalinities were investigated. SEM, NEXAFS, and STXM were used to observe particle morphology and alkaline Na speciation and distribution. Gypsum combination promoted leaching of Na-bearing solids and the replacement of exchangeable Na. The use of organic citric acid to transform bauxite residue alkalinity.ABSTRACT: Bauxite residue (BR) is a highly alkaline solid hazardous waste produced from bauxite processing for alumina production. Alkaline transformation appears to reduce the environmental risk of bauxite residue disposal areas (BRDAs) whilst potentially providing opportunities for the sustainable reuse and on-going management of BR. Mineral acids, a novel citric acid and a hybrid combination of acid-gypsum treatments were investigated for their potential to reduce residue pH and total alkalinity and transform the alkaline mineral phase. XRD results revealed that with the exception of andradite, the primary alkaline solid phases of cancrinite, grossular and calcite were transformed into discriminative products based on the transformation used. Supernatants separated from BR and transformed bauxite residue (TBR) displayed distinct changes in soluble Na, Ca and Al, and a reduction in pH and total alkalinity. SEM images suggest that mineral acid transformations promote macro-aggregate formation, and the positive promotion of citric acid, confirming the removal or reduction in soluble and exchangeable Na. NEXAFS analysis of Na K-edge revealed that the chemical speciation of Na in TBRs was consistent with BR.Three acid treatments and gypsum combination had no effect on Na speciation, which affects the distribution of Na revealed by sodium STXM imaging.

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Section: Introductionmentioning

confidence: 99%

Acid transformation of bauxite residue: Conversion of its alkaline characteristics

Kong

Xue

et al. 2017

Journal of Hazardous Materials

131

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“…In fact, many researchers have conducted tests on the potential use of waste materials in fired clay bricks. The temperature gradient of the firing has highly effected the brick porosity since various minerals in the waste materials and clays dissolved at different temperatures [39][40][41]. Subsequently, firing temperature of higher than 850 degree caused speedy and irreversible decay of the clay bricks [37].…”

Section: Methods Of Producing Brickmentioning

confidence: 99%

A Review on Characterization of Sediments for Green Bricks Production

Ean¹,

Malek²,

Mohammed

et al. 2018

IJET

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Accumulation of dredged sediment has raised environmental concern in various countries. Recycling of sediment into bricks is a viable solution to the environmental pollution. Concerning to the utilization of sediment in bricks, this study reviews the needs of characterization on sediment and methods of producing sediment bricks. Particle size distribution was found to be the key criteria for characterization of sediment. Sizes of particles determined the function of the sediments in the bricks. In spite of that, leachability of heavy metals is another important aspect for contaminated sediment. Cementing bricks used cementing materials as the stabilization agent to the heavy metals. It is necessary to conduct leaching test for the end-product of the sediment to ensure the heavy metals leached are within the regulatory limits. In conclusion, method of producing sediment bricks may vary due to the various characteristics of sediment for a promising environmental friendly production.

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“…Currently, almost all bauxite residue is stored indefinitely in land-based bauxite residue disposal areas (BRDAs) (Burke et al, 2013;Zhu et al, 2016a), which require continuous resources to manage and transform the waste and reduce its potential to contaminate water and land, as well as the surrounding ecology (Banning et al, 2014;Lockwood et al, 2015;. Leaching of alkaline waste is a further potential problem (Buckley et al, 2016;Pulford et al, 2012;Samal et al, 2015). The adverse alkalinity means that bauxite residue is listed as a contaminated waste, which limits its disposal, applications and options for its sustainable reuse.…”

Section: Introductionmentioning

confidence: 99%

Natural evolution of alkaline characteristics in bauxite residue

Kong

Guo

Xue

et al. 2017

Journal of Cleaner Production

115

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Bauxite residue, a highly alkaline solid waste, is extremely hazardous to the surrounding environment and current research approaches have largely focused on the removal and separation of alkaline substances. Natural weathering processes may be a step forward in terms of their regeneration. In this study, natural evolution of basic alkalinity, electrical conductivity, exchangeable ions and acid neutralizing capacity of residue in the disposal areas is discussed. Minerals, exchangeable cations and alkaline anions were analyzed by X-ray powder diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and titration, respectively. Acid neutralizing capacity was carried out by batch neutralization experiments. Basic alkalinity, electrical conductivity, cation exchange capacity and exchangeable sodium percentage decreased with increasing disposal duration. Sodium was the predominant exchangeable cation in fresh residue but its concentration significantly decreased with increasing time from initial disposal. The acid neutralizing capacity of bauxite residue was investigated by incubation with hydrochloric acid. Acid neutralizing capacity curves changed with disposal duration and each revealed a characteristic buffering behavior that could be controlled by its alkaline components.

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Characterization and microstructure observation of sintered red mud–fly ash mixtures at various elevated temperature

Cited by 45 publications

References 11 publications

Acid transformation of bauxite residue: Conversion of its alkaline characteristics

Acid transformation of bauxite residue: Conversion of its alkaline characteristics

A Review on Characterization of Sediments for Green Bricks Production

Natural evolution of alkaline characteristics in bauxite residue

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